Automatic circuit breaker



Dec. 17, 1940. SACHS AUTOMATIC CIRCUIT BREAKER Filed Feb. 27, 1959 frills Il 4V 1 LAR.

gianna uw.' i1, 1940"*v PATENT OFFICE n 2,224,990 AUTOMATIC omcm'r nimma Joseph Sachs, West Hartford, Conn., assignor to Colts Patent Fire Arms Manufacturing Company, Hartford, Conn., a corporation of Connecticut Application February 27, 1939, Serial No. 258,701

3 Claims.

This invention rela'tes to a circuit breaker of the general type disclosed in my Reissue Patent No. 20,018 and in my Patent No. 2,020,333, each entitled Automatic circuit breaker. In a circuit breaker of the said type there is a bodily movable current-carrying bi-metallic latch which serves as at least a part of the mechanical con-v nection between the handle or operating member and the movable contact carrying member. In order to keep manufacturing costs at a minimum it is desirable to use one size and style of mechanism for a relatively wide range of electrical capacities. The electrical capacity of the circuit breaker can be widely varied by changing the size and characteristics of the movable bimetallic latch, but there are definite limits as to the minimum size of the latch inasmuch as the latch must in any event have sufficient mechanical strength to operate and control the movable contact member.

' When a circuit breaker of relatively large size is to be given a very small current capacity, it may be diilicult or impossible to yprovide a bi- .,'metallic latch which is suillciently strong mechanically and which is at the same time suiciently sensitive to be heated and deected by a relatively small overload current. The general object of this invention is to provide a circuit breaker which avoids the diiculties above pointed out, this being accomplished by changing the electrical connections so that` no current passes through the bi-metallic latch itself, the said latch being heated solely by 4a separate currentcarrying heating element Aclosely adjacent thereto. This makes it possible for the latch to be relatively large to provide the required mechanical strength, thev heating element being so designed as to effect heating -as the result of a relatively small overload current.

In the accompanying drawing I have shown one suitable embodiment of the invention, but it will be understood that the drawing is intended for illustrative purposes only and is not to be construed as defining or limiting the scope of the invention, the claims forming a part of this speciiication being relied upon for that purpose. f

Of the drawing:

Fig. 1 is a front view of a circuit breaker embodying the invention.

Fig. 2 is a view similar to Fig. 1, but with the iront insulating cover omitted.

Fig. 3 is a transverse sectional view taken along the line'lof Fig. 4.

Fig. 4 is a longitudinal sectional view taken (Cl. 20D-122) vwhich they occupy at the beginning of the automatic circuit-opening operation.

Fig. 7 is a view similar to Fig. 6, but showing the movable parts in different relative positions. 10 Referring to the drawing, i represents the main insulating base or support which carries all of the other parts of kthe circuit breaker. Fitting the support I at the front thereof is an insulating cover 2. The rear support is of box-like 15 form, being substantially closed at all four sides and at the bottom. The front cover is also of y more or less box-like form, having a recess open at the bottom into which certain parts of the mechanism project. When the two parts l and 20 2 Aare assembled as shown, there is provided an .metallic plates 3, 3 which .are held in place by means of screws 4, l extending forward from the rear of the support. 'Ihe plates 3, 3 are provided with integral rearward extending portions 3*, 3, 30 Carried by the said rearward extensions, 3 and extending transversely between them is a pivot pin 5. Pivotally mounted on the pin 5 is a contact carrying member which includes two parallel-plates 6, 6 spaced apart transversely and 35 suitably connected together to move as a unit. These plates have aligned bearing apertures through which the pivot pin 5 extends, shoulders on the pin serving to hold the plates in proper spaced relationship. Suitable spacing 40 washers, not shown, hold the plates in p21-oper spaced relationship to the supporting plate extensions 3, 3*.

The two plates 6, 6 serve to carry the main' movable contacts 1 and 8 of the circuit breaker, 45 each 'of which extends from one to the other of the two plates 6, t and is in direct engagement A with both of them. Each of the said plates 6 is provided with apertures adapted to receive simi- I larly shaped lateral projections on the corre- 50 spending contact. When the said projections on and held in spaced relation by means of insulating members 3 and I8 which are structurally separate from the plates. The plates are notched to receive projections II, I2, I3 and |4iormed 5 on the insulating members and the two plates and the insulating members are held in proper relationship by means of tie rods or rivets I8, |8. The plates 8, 8 have arcuate outer edges concentric with the pivotal axis at I and the insulating members 9 and |0-are externally shaped to conform to these arcuate edges. It will be apparent that the insulating members 9 and I8 extend transversely from plate to plate and that the movable contact 1 extends through the space between the two members. The member 9 engages with the other movable contact 3 and thus extends circumferentially from one contact to the other.

Carried by the movable contact member is a bi-metallic thermostatic strip I8 and this is shown as being connected directly with the contact 1, but there may be variation as to the manner oi' mounting or attaching the said strip. The

strip I8 is provided at its projecting end with a lug I1 which enables the strip to serve as a latch as will be presently explained.

A heating element I8 is provided which electrically connects the two movable contacts 1 and 8. This is preferably a wire bent to a serpentine form as shown in Fig. 5, and it is positioned closely adjacent the strip or latch I8, so that heat from the element I8 is transmitted to the latch.

Carried by the insulating support I are two substantially stationary main contacts i 9 and 28 which are connected with the said ysupport by means of more or less resilient bent conducta ing straps 2| and 22. These stationary contacts |9 and 28 are so positioned and arranged that they can be firmly engaged respectively by the two movable contacts 1 and 8 as clearly shown in Fig. 3. 'Ihe o uter end of the supportingstrap 2| engages the bottom wall of a recess in the support I and the said strip is held in place by means of two screws 23 which also hold a conductor 24. This conductor projects from the circuit breaker at the right and may be connected at 24' directly with the bus bar of a panel board or may be provided with a suitable wire engaging terminal. A rearward projection 2 on the cover 2 normally substantially lls the last said recess in the main support. The outer end of the conducting strap 22 engages the bottom wall of a recess in the main support I and y is heldin place by screws 28 which also hold a laterally extending conductor 28. The conductor 26 is provided with a wire terminal 26* and suitable recesses 21 are formed in the upper left hand corners of the support I and oi' the cover 2 to permit access to the said wire terminal. A separate insulating block 28 normally substantially fills the last said recess in the main sup' port.

From the foregoing description it will be apparent that pivotal movement of the contact member serves to bring the movable contacts 1 and'8 into or out of engagement with the respective stationary contacts I9 and 28 to make or break the circuit. When the parts are in the contact engaging position as shown in Fig. 4 electrical connection is established between the conductor or terminal 24 and the terminal 26". Springs 29, 29 are provided for biasing the member in the contact disengaging or circuit-open- 75 ing direction, these springs surrounding the pin 8 and being positioned between the supporting plate extensions 3*, 3 and the'insulating plates 8, 8.

For actuating the contact member for normal switching purposes or to eii'ect closing of the circuit after automatic opening thereof, there is provided an actuating member or actuator 38, which is normally engaged by the thermostatic strip or latch I8. The actuator 38 is pivoted to the contact member i'or movement about a bodily movable axis, and it is of bell crank form and consists of two spaced metallic plates pivotally mounted on a pin 3| extending transversely between the two side plates 6, 8. A transverse pin 32 serves to limit relative movement of the actuating member in the counter-clockwise direction. The actuating member is provided with a transverse pin or roller 33 which, at normal temperatures, is engaged by the lug I1 on the thermostatic latch I 6. With the parts in the relative positions shown in Fig. 4, the actuator and the contact member are positively connected to move in unison.

For manually operating the actuator 38 I provide a handle member 34 which is mounted on a pin 35 extending transversely between the supporting plates 3, 3. The handle member pro- `iects through a suitable opening in the front wall of the front cover 2. A spring 36 is provided which serves to bias the handle toward its opencircuit position, that is, in the counterclockwise direction `from the position shown in Fig. 4. The handle member 34 is connected with the actuator 38 by means of two similar links 31, 31, the links being pivoted to the handle members at 38 and to the actuator at 39.

When the parts are in the relative positions shown in Fig. 4 the links 31 cooperate with the handle member 34 to form a toggle which locks the parts in position with the movable contacts 1 and 8 pressed into iirm engagement with the stationary contacts I9 and 28. Continued movement of the handle in the clockwise direction s prevented by the engagement ci an extension 34* thereon with a pin 48 extending transversely between the plates 3, 3. The pivotal axis at 38 is above a straight line connecting the pivotal axes at 35 and 39, and thus the handle member 34 and the links 31 serve to resist the tendency of the contact member to move in the clockwise direction under the iniiuence of the springs 28 and of the resilient contact supporting strips 2| and 22. At the same time the said toggle action holds the handle 34 in its right hand or closed-circuit position, resisting the tendency of the spring 36 to move the handle member in the counter-clockwise direction.

The above-described toggle action can be released by pressing the handle toward the left,

the parts then moving under the action of the springs 29 and 3B to their open-circuit positions. The movable contacts 1 and 8 are thus disengaged from the stationary contacts I9 and 28 and the circuit is broken in two separate places. By moving the handle toward the right the several parts can be restored to their respective positions, as shown in Fig. 4, and the circuit can be thus reestablished.

As already explained the heating element I8 is electrically connected between the contacts 1 and 8 and is adjacent the latch I 6. Upon the attainment of an excess current condition in the circuit which causes more than normal heat- 'ing oi the element I8, the latch I8 is deflected member 34 and of the links 31.

lug l1 is disengaged from the pin or roller 33, such disengagement being shown in Fig. 6. This disengagement or partial disengagement permits the actuator 30 to turn slightly relatively to the contact member and in the clockwise direction. This slight clockwise movement reduces the pressure which had theretofore served to hold the links 31 and the handle member 34 in their effective toggle relationship. This reductionl in pressure permits the handle member 34 to move in the counter-clockwise direction so as to render the toggle ineffective. By reference to Fig. 6 it will be observed that the pivotal axis at 38 has moved below the dot-and-dash line connecting the pivotal axes at 35 and 39, thus freeing both the contact member and the handle member so that they are. automatically moved to their open-circuit positions under the influence of the springs 29 and 36. It will be understood that the contact member and the handle member move substantially simultaneously, the lug -'I1 and the pin or roller 33 perhaps never becoming completely disengaged from each other. When the parts reach their full open-circuit position, the lug i1 and the pin or roller 33 can contact member is not in any way dependent on the circuit-opening movement of the handle member and will, in fact, occur even though the handle member be held in its closed-circuit position, as shown in Fig. 7. The downward or outward deflection of the thermostatic strip I6 permits the actuator 30 to turn in the clockwise direction as already stated, thus releasing-the contact member from the control oi the handle The contact member moves in the clockwise direction to the position shown in Fig. '1, the actuator 30 and the links 31 assuming the relative positions shown in that figure. If the handle 34, after having been held as described, be now released. it will move under the iniiuence of the spring 3B to its open-circuit position, thus bringing the actuator -30 into its normal position with respect to the contact member so that the pin or roller 33 can be engaged by the lug I'I.v

While the latch I3 may be electrically connected with the contact 1 as shown, this is merely to facilitate manufacture, and inasmuch as there is no electrical connection with the other end of the latch, no current ilows therein. The latch can be of such size as to have ample mechanical strength. The heating element I3 may have a very high resistance so as to be heated to a high temperature by even a rather small overload current.

What I claim is:

1. 'I'he combination in an automatic circuit breaker, of a movable contact member biased in the circuit-opening direction and including an electric contact, a stationary electric contact engageable by the movable contact. releasable iiection of said strip.

mechanism normally holding the contact member in closed-circuit position, a bodily movable thermostatic bi-metallic strip forming part of said mechanism and rigidly connected ai; one end with the movable contact member and capable of deilection to cause the other end to relatively move and thereby effect the Vrelease ofv the mechanism, and a bodily movable heating element separate from the bi-metallic strip and electrically connected with said movable contact and positioned closely adjacent the bi-metallic strip so that upon the attainment of an abnormal current condition in the circuit the heating element transmits suili'cient heat to the strip to.

cause deection thereof relative to said heating element and releasable mechanism to effect release of said mechanism.

2. 'Ihe combination in an automatic circuit breaker, of a movable contact member biased in the circuit-opening direction and including two spaced electric contacts, two stationary electric contacts engageable by the respective movable contacts, releasable mechanism normally holding the contact member in closed-circuit position, a bodily movablethermostatic bi-metallic strip forming part of said mechanism and rigidly'connected at one end with the movable contact memberand capable of deflection to cause the other end to relatively move and thereby eiect the release of the mechanism, and a bodily movable heating element separate from the bimetallic strip and electrically connecting the two contacts and positioned closely adjacent the bimetallic'strip so that upon thev attainment of an abnormal current condition in the circuit the heating element transmits suflicient heat to the bi-metallic strip to cause deflection thereof relative to said heating element and releasable'mechanism to eiect release of said mechanism.

3. The combination in lan automatic circuit breaker, of a movable contact member biased in the circuit-opening direction and including two spaced electric contacts, two stationary electric contacts engageable by the respective movable contacts, a heating element electrically connecting the movable contacts and bodily movable therewith and with the movable contact member, releasable mechanism normally holding the contact member is closed circuit position, a thermostatic bi-metallic strip independent oi.' saidtallic strip being disposed in proximity to the.

heating element with its major portion free to move relative to said heating element when deilected upon attainment of abnormal current conditions in the circuit, and the other end of said bi-metallic strip being operatively engageable with the releasable mechanism whereby the bi-metalllc strip forms a part thereof to eiiect releasing movement of the mechanism upon de- JOSEPH SACHS. 

